1. Field
Exemplary embodiments of the present invention relate to a method for fabricating a semiconductor device, and more particularly, to a method for fabricating a semiconductor device, which can prevent an etching defect caused in a process of fabricating a magnetic tunnel junction pattern.
2. Description of the Related Art
A dynamic random access memory (DRAM) is a representative semiconductor memory having characteristics of high-speed operation and high integration. On the other hand, the DRAM being a non-volatile memory loses data when power is turned off, and refresh of data is continuously performed during the operation of the DRAM. Therefore, the DRAM has a large power loss. On the other hand, a flash memory, while having characteristics of non-volatility and high integration, has a slow operating speed. As another example of a semiconductor memory, a spin transfer torque random access memory can be highly integrated while having characteristics of non-volatility and high-speed operation.
The spin transfer torque random access memory refers to a non-volatile memory that stores data in a magnetoresistive element using a change in magnetoresistance depending on a magnetization direction between ferromagnetic substances. In the magnetoresistive element, the resistance of a cell is decreased when the spin directions (i.e., magnetic momentum directions) of two magnetic layers are identical to each other, and the resistance of the cell is increased when the spin directions of the two magnetic layers are opposite to each other. Accordingly, data is stored using the fact that the resistance of the cell is changed depending on a magnetization state of the magnetic layers in the magnetoresistive element. As the magnetoresistive element, a magnetic tunnel junction (MTJ) may be used.
The spin transfer torque random access memory with an MTJ structure is generally formed as a structure in which a first ferromagnetic layer, an insulating layer and a second ferromagnetic layer are laminated. When electrons passing the first ferromagnetic layer pass through the insulating layer used as a tunneling barrier, the tunneling probability is changed depending on a magnetization direction of the second ferromagnetic layer. That is, tunneling current is maximized when the magnetization directions of the two magnetic layers are parallel to each other, and the tunneling current is minimized when the magnetization directions of the two magnetic layers are opposite to each other. For example, it may be determined that ‘1’ (or ‘0’) is recorded as data when resistance set by the tunneling current is large and ‘0’ (or ‘1’) is recorded as the data when the resistance set by the tunneling current is small. Here, one of the two magnetic layers is referred to as a fixed magnetic layer and has its magnetization direction fixed, and the other of the two magnetic layers is referred to as a free magnetic layer and has its magnetization direction reversed by an external magnetic field or current.
Since the spin transfer torque random access memory is in the initial process of development, there are several issues to be addressed in a patterning process. For example, in a process of patterning and subsequently cleaning a magnetoresistive element, a tunnel insulating layer interposed between two ferromagnetic layers may be lost or the ferromagnetic layer may be exposed to the outside. Therefore, it is useful to develop a process of fabricating the spin transfer torque random access memory that addresses such issues.